Method for producing an aggregate-lined



July 31 1956 M. G. BURWELL METHOD FOR PRODUCING AN AGGREGATE-LINEDCORROSION-RESISTANT HOT WATER TANK Original Filed March 1'7. 1951 2Sheets-Sheet 1 INVENTOR ATTORNEY y-- 1956 Y M. G. BURWELL' Re. 24,187

METHOD FDR PRODUCING AN AGGREGATE-LINED CORROSION-RESISTANT HOT WATERTANK Original Filed Ma1 0h 17. 1951 2 Sheets-Sheet 2 INVENTOR Mddi'fiZ6} Jar-well ATTORNEY METHOD ma LINED CORROSION-RESISTANT HUI WATER OwlN0. 2,7,2'2, dated 1 '25, 1955, Serial 11-,114, March 17, 1951. for useI W! 1, 1955, 8G! N0- 5,310

I Chill. (Cl. 117-64) Mattea'udoaedinheavybraeketalflappearslnthepateatbatformanopartofthlarelssuespedflmatterprhtedhlitallcaindlcatestheaddltionsmadebyrel-e. I

The present invention relates to hot water tanks, range boilers, and thelike, and more particularly to an improved aggregate-lined hot watertank and method for producing the same.

In the past, it has been proposed to line the interior surfaces of hotwater tanks, range boilers, and the like with corrosion-resistantmaterials, such as glass, enamel, and cement, to protect the innersurfaces of the metallic tank from direct contact with water introducedtherein, and thereby to prevent corrosion and rusting of such tank andthe consequent undesirable contamination of the hot water source withrust deposits. However, hot water tanks having non-corrosive innerlinings are subject to numerous objections, primary of which is therelatively high cost of such tanks, and also the relatively fragilenature of the inner lining material which is easily cracked or brokenduring shipment or handling of such tanks, or which may be destroyedwhen the outer surface of the tank is subjected to impact forces orsharp blows. Also, prior hot water tanks embodying a cement lining havebeen found to be entirely impractical due to the shrinkage of theconcrete inner lining material after initial application thereof to thewalls of the tank and during curing of the applied cementitious mix,with the result that the inner lining separates from the inner surfacesof the metallic tank structure and is subject to relative displacementwithin the tank, thus rendering the same easily broken or cracked andincapable of withstanding the normal pressures exerted by waterintroduced therein under municipal water main pressures.

The primary object of the present invention, therefore, is to provide ahot water tank having an inner lining of corrosion-resistant cementiousaggregate material which is so applied as to cover completely the entireinner surface of the metallic tank and maintain its relative position inabutting relation to the side walls of the tank, thereby preventingrelative displacement between the inner surfaces of the tank and theinner lining upon curing or hardening of the latter. A further object isto provide an aggregate lined tank wherein the inner lining possesses aninherent toughness suflicient to prevent cracking or breaking of thelining due to impact forces normally encountered during shipment andhandling of the tank.

It is another object of the invention to provide an efficient and.economical method for applying an inner aggregate lining to metallictanks, whereby the manufacturing cost of such tanks is materiallyreduced in comparison with the usual glass or enamel lined tanks.

A further object of the invention is to provide an im proved innerlining material for metallic tanks which may be efllciently andeconomically applied to the inner surfaces of metallic tanks, andwherein the curing of the inner lining material iseffected'substantially concurrently raonucmc, AN accnnca'ra- ReiaauodJuly 31, 1956 with the application of such material to the innersurfaces of the tank, thus eliminating shrinkage of the lining mate'rialwithrespecttothetankstructureandenablingsuch tanks to be produced insubstantially continuous highspeed operations.

.Astillfurtherobjectoftheinventionistoprovidea method for producinginner-lined metallic hot water tanks,

wherein the components of the inner lining material or composition areintroduced [and intimately admixed] within the unlined tank andthereafter forcibly applied and compacted against the inner surfaces ofthe tank by centrifugal forces established by relatively high-speedrotation and simultaneous vibration of the tank,'whereby to deposit auniform thickness or layer of corrosion-resistant material over theentire inner surface of the tank.

For a further and more detailed understanding of the present inventionand the various additional objects and advantages realized therefrom,reference is to be had to the following description and the accompanyingdrawing, wherein:

Fig. l is a diagrammatic view of a machine employed in the applicationof a resinous coating material to the inner surfaces of the tank bodypreparatory to applying the aggregate inner liner;

Fig. 2 is a diagrammatic vertical sectional view showing the applicationof the mineral aggregate to the head closure member of the tank;

' Fig. 3 is a perspective view of a tank-resting and tilting machineutilized in the step of mixing the aggregate lining material;

Fig. 4 is a transverse vertical sectional view taken through the tankduring the mixing of the components of the aggregate lining materialtherein;

Fig. 5 is a similar view taken through the tank and showing thecentrifugal application of the aggregate mix against the interior sidewalls of the tank; [and] Fig. 6 is an enlarged fragmentary verticalsectional view taken through the tank and its inner lining; and

Fig. 7 is a diagrammatic top plan view of a tank and the associatedvibration-producing flailing devices.

In accordance with the present invention, I make use of a metallic hotwater tank 9 comprising a cylindrical openended body 10 and top andbottom members 11 and 12, respectively. In the usual manner, thecylindrical body portion 10 may be formed from a single sheet which isrolled and bent into the cylindrical configuration as shown,

. and which has the abutting longitudinal edges thereof welded togetherto provide an elongated cylindrical shell.

- tion l0 toclose the same. It will be understood that the end closuresl1 and 12 are rigidly connected with the cylindrical body portion 10 asby welding or other suitable means providing fluid-tight connectiontherewith.

In preparing a metallic tank for lining operations, the inner surfacesof the cylindrical body 10 and the end closures 11 and 12 are appliedwith a relatively thin coating or layer 14 of a hardenable resinousmaterial, such as one of the phenolic base resins or one of thehardenable asphaltic base resins, in order to cover completely the innersurface of the metal. This application of the resinous material, asshown in Fig. l, is preferably carried out under'relatively highpressures to assure permanent adhesion between the resinous material andthe inner surface of the tank and to eliminate the necessity of firstcleaning or finishing the interior surface of the tank to secure a goodbond between the resinous coating and the metal of the tank. It shouldhere be understood that by applying a phenolic base resin, such as aliquid form of phenol-formaldehyde, to the inner surfaces of the tankunder superatmospheric pressures, the liquid coating materialis forciblyapplied to" the innerwalls Y Y the tanktodisplace adhering. foreignmatter or dirt posed upon'the inner surfaces of thegtankaad thereby todirectly contact the metal of the tank itself, Thus,

theresinous-coatin'g material functions to seal any cracks or crevicesthe inner surface of tank, andis prevented later scaling or 'spallingdue to .the pnor displacement of any dirt or foreign matterfrom the'inner wall surfacesof the tank. The step of applying the t'esinouscoating 14 to the-inner surfaces of the-tank is 'aticallyillustrated inFig. l of the-'drawing, 1

wherein the numeral 15 designates generally a tankspectiveends bytransversely disposed end plates 11, and

One of the end plates 1! of the frame IS-is'proyided with a flatinwardly extending sealing plate 21 in which is formed an annulargroove, at 2 2, to receive an open' end of the tankwhich may, or'maynot, have its associated end wall closure secured thereto is received'within a cavity formed in a spring-pressed'head 23. n The 23 issupported on a shaft 2.4which.s'lidaltly extends;

through an opening formed in the-opposite endplate; 11,

and mounted between the head Z3-and end jplate'lll is compression-spring.2 5 which is arranged (0 -931]. iently urge the head 23jinwardly offrame and thereby to releasably support the tank within the. frame fortilting or rocking movement therewith The spring-pressed head. 23additionally-serves to tightly seal the opposite open; end of ;the tank'groovefl ofthesealingplaltell." v I When it is desired'to applythecoatingll' to the inner surfaces of the metal tank, -a'given quantityof liquid uncured resinous material, commensurate with the 1 desiredthickness of coating, is introduced within the interior of the .tankbyway of one of the pipe-receiving openings 26 provided in thebodyportion 10 for the reception of the usual inlet and outlet pipes orconduits associated with the ordinaryside-arm heater tank,'or one of thepipe-receiving openings provided in the underfired type of tank. Afterintroduction of "theliquid coating material within the tank, the variouspipe-receiving openings are plugged to seal the interior of the tankagainst the escape of fluids. Thereafter, compressed air-derived from acompressor or pump P is'introduced within the tank by way of a flexiblehose or conduit 27 which extends from thepump outlet to a conduitconnection 28 extending through the end plate 17 and the sealing plate21 and communicating with the open end of the tank It). I The pressureexerted within the .inter'ior of the tank I ranges preferably between 50and 80 p. s. i., and while this pressure is present within the tank, thesame is rocked or tilted back and forth in conjunction with the frame15.

to evenly distribute the liquid coating material over the entire innersurface of the tank body and to provide thereon a relatively thin filmof the uncured viscous liquid. It is important to note thattheapplication of relatively high pressures to the interior walls'of thetank, in addition to providing an elficient means for applying thecoating material, alsoserves as a means for testing the tank structureto detect leaks. In the event that the end ofthe cylindrical body is orthe tank. ms opposite .2

within the annular in artisan, of he -':leaks Tamas and thereby tosealthet thesame is placed infa'cui-ingoven to cure and set the resinouscoating 14. The innersurfaces of the top and resinous material,preferably under pressure, and there- 7 after cured at of thetank.

i ,the interior surfaces'of'the closure bers, a cementitious aggregatemix is then applied to the" Stop and bottom closures.-' lngeneralpractice,.the'tank body-1Q hasithe upper ortopelosure llwelded theretoprior v to. the application of the material,

.but the bottomfend closure l2 .is'removed prior to coating toprovideaccess to the interior surfaces-of the body position, and with thepipe-receiving openings of. the

normal thickness offthe' cementitious layer 30. the cementitiousaggregate layer 30 is deposited the treat d an; a. similar ma ner"ariplrfmma' the usual side-arm heater type cloaur'e llpfanunderfired-type.

lain or the like, is not o1 apply-a c'ejrnentitious aggregate liningthereto, in view of the fact that the bottom of such undertiredoriginally formed from, or are provided with of, corrosion-resistantmaterials.

Following thes'teps of applying the aggregate inner lining to the topand bottom closures, where necessary, the lining material is permittedto set and solidify. Thereafter, the bottom end closure lz'is welded tothe tank body 10 to close the interior thereof, with the exception ofthe normal pipe-receiving openings 26. Prior to'or following, thewelding of the end closure 12 to the tank body, a quantity of sand maybe introduced within the body 10.

I is then placed upon a mixing machine 34 which is illustrated indiagrammatic form in Fig. 3 of the drawing. The mixing machine comprisesa frame 35 which is 'end portions rot'atably supported instationary-hearing frames 37. A crank arm 38 is connected with one endof the shaft 36 and serves to impart oscillating movement to the shaftin response to reciprocatingmovement of a connecting rod 39 which isconnected .to be reciprocated by a motor or engine and an associatedmotion-trans- I mitting drive, not shown. Extending longitudinally ofthe frame 35, and journaled therein for axial rotation, are a pair ofspaced parallel shafts 40, each of which carries, at spaced longitudinalintervals, a pair of-cradle wheels or rolls 41 which provide a cradlebed for the tank bodylt). Connected with one of the shafts 40 is a drivepulley or gear 42 which is arranged to be driven by a continuous belt orchain 43 which is drivingly connected with a reversible power course,not shown. In operation,

. After tilting of the ta'nk land inspection thereof for leaks, thepressure within the body is' relieved and bottom-closures 11 and 12 aresimilarly .coated with the elevated" temperatures withinAfterapplication f the material to l ttand topjclos te 1 with the tankbody in an inverted closure plugged by screw-threaded spuds 21 I which-p rojcc't'inwardly. through the openi gs- 26 and beyondfthe' terinner'surface of the closure 11, the same is troweled to l a unifomithicknessby means of a: rotary 'troweling head .32'wh'ichis formed soas to'enterthe open-endof the;

interior of the tank as a component part of an aggregate mix which, aswill be hereinafter more fully explained, provides the entire innerlining material for the tank The tank, with its end closures l1 and 12welded thereto, 1-.

rigidly carried on a trunnion shaft 36 having its respective sins? themachine 34 serves to impart both reversible axial rotation andlongitudinal tilting movement to the tank 9 when the latter is placedthereon as shown in Fig. 3.

Thus, the machine34 and the tank 9 form, in effect, a mixing andagitating machine similar in operation to the usual concrete mixer.

' of the conduit-receiving openings 26 of the tank. Followingintroduction of the sand component of the aggregate mix within the tank,a wet cementitious slurry comprising water, Portland cement, and acuring'accelerator is introduced within the tank to provide acementitious aggregate mix comprising approximately'by weight:

60 parts sand, 15 parts water, 20 parts Portland cement, and

e 2 parts accelerator (based on NaaSiOa) All of the pipe-receivingopenings of the tank are then 'plugged and the machine 34 is energizedto rotate the tank and to tilt the same longitudinally. In this manner,the separate components of the aggregate mix are thoroughly admixedtogether within the interior of the tank, as shown diagrammatically inFig. 4 of the drawing. Preferably, the machine 34 is operated to firstimpart I simultaneous rocking and rotation to the tank, with thedirection of rotation being reversed after approximately five rotationsin either direction, until the separate sand, water, cement, andaccelerator components have become thoroughly mixed. Then the machine isconditioned to stop the tilting movement thereof while permitting thetank to rotate about a horizontal axis. This final rotation dispersesthe mix evenly throughout the length of the tank and prevents an undulylarge accumulation of the mix at any one point in the tank.

After mixing of the aggregate, the machine 34 is stopped and the tank 9containing the aggregate mix is transferred from'the mixing machine to acombined spinning and vibrating machine, not shown, which engages andsupports the tank at its ends, and imparts relatively highspeed axialrotation to the tank while the latter is maintained in a substantially[horizontally] horizontal plane. Fig. of the drawing illustratesdiagrammatically this step. In the spinning operation, the relativelyfluid aggregate mix within the tank is deposited by centrifugal forcescaused by the relatively high-speed rotation (approximately 350 R. P.M.) against the inner wall of the tank body 10. Simultaneously with thespinning of the tank, the latter is subjected to vibrational forcestransmitted to the tank by means of a multiplicity of rotary flailingdevices 45 which are arranged to strike the outer surface of the tankbody along a line extending substantially throughout the length of thetank. Each of the flailing devices 45 comprises a plurality of outwardlyprojecting striking arms 46 which are pivotally connected at their innerends to a wheel 47 carried upon a common drive shaft 48. The shaft 48 isarranged adjacent to the outer wall of thetank body and extends inparallel coextensive relation thereto, with each of the flailing devicesbeing carried at relatively closely spaced intervals along the length ofthe shaft 48. In carrying out the spinning operation, the tank is firstrotated for approximately five to eight seconds before subjecting thesame to vibr tion.

Thispermits the aggregation to be forcibly deposited in a uniform layer50 against the inner wall of the tankioody prior to vibrating, at whichtime the flailing eviccs are energized to impart relativelyhigh-speed'vibrations to the tank which serve to compact and densify thelayer 50 of aggregate mix against the inner wall surface. After apredetermined spinning and vibrating cycle (approximately fifteenseconds), the tank is permitted to come to therefrom, to -permit excesswater originally contained in and expressed from the mix during theinitial spinning and vibrating cycle to drain from the interior of thetank.

After the excess water has been permitted to drain from the interior ofthe tank, the plug or spud is again placed within the pipe-receivingopening 26 to close the interior of the tank, and a second spinning andvibrating cycle is commenced and continued for another period ofapproximately fifteen seconds. At the end of the second spinning andvibrating cycle, the aggregate mix has become completely cured due tothe removal of the excess water and the action of the [currihglcuringaccelerator incorporated in the mix at the time of introduction withinthe tank. It is important to note that the second cycle of spinning andvibrating is timed so as to occur simultaneously with the curing andhardening of the aggregate mix, in order that the inner lining 50 of thetank, following the second spinning and vibrating cycle, is completelycured, hardened, and set.

The tank is thereafter removed from the spinning and vibrating machineand the spuds or plugs 31 removed from the various pipe-receivingopenings thereof, and with the tank positioned in a vertical or uprightposition, any remaining excess fluids or water within the tank ispermitted to drain through the pipe-receiving openings. The tank, withits inner lining of aggregate, is then in condition for use, as theinner lining material has completely hardened and set in firm directadherence with the layer of coating material 14 previously applied tothe inner wall surfaces of the tank body 10.

The curing accelerator used in the present aggregate mix preferablycomprises sodium silicate, or water glass, and functions to greatlyspeed the setting or curing of the aggregate cementitious mix, and makespossible the complete curing of the layer of inner material during thesecond and last spinning and vibrating cycle. It is believed that uponremoval of the excess fluids or water originally contained within themix and expressed there from during the initial spinning and vibratingcycle, the curing accelerator acts as an adsorption agent for the liquidor oisture which remains within the layer 50 of aggregate after the sameis initially applied by centrifugal forces to the inner walls of thetank 10. Thus, the integrally contained moisture within the mix isadsorbed by the curing accelerator which is dispersed evenly through themix comprising the inner layer 50 of the tank, and tests have shown thatthe layer of inner lining material 50, immediately following the secondand last spinning and vibrating cycle, is completely set and hardened,thus eliminating the necessity for subsequent curing which, in the caseof an ordinary cementitious mix, would require in the neighborhood ofseventy-two hours, and would additionally permit the inner layer 50 toshrink away from direct contact with the inner wall of the tank. Thus,by effecting a complete cure of the aggregate inner lining during thelast vibrating and spinning cycle, when the material comprising theinner lining isbeing forcibly pressed against the inner wall of thetank, there is no shrinkage whatsoever between the inner lining materialand the interior surface of the tank. This results in a substantiallyintegral bond between the inner surface of the tank and the inner lineror layer 50, and tests have shown that the tank containing the innerliner may be dropped from relatively extreme heights without in any waycracking or breaking the inner liner from the interior tank surface.

It is also important to note, with reference to' Fig. 6 of the drawing,that the simultaneous high-speed spinning and vibrating operation causesthe aggregate inner lining material to assume a definite and distinctstrata formation. As shown in cross section in Fig. 6, that portion ofthe layer 50 which lies adjacent the relatively thin coating layer 14 ismade up of the heavier particles of the aggregate mix which aredispersed in relatively widely spaced relation to provide a somewhatporous stratum, while the outer stratum 52 of the layer 50 is made up ofrelatively finely divided lightweight aggregate materials which providea denser outer surface layer which comes into contact with the waterintroduced within the tank. It will be understood, of course, that theparticles of the mix comprising the relatively porous stratum 51 areintegrally bonded together by the cement a good insulating layer betweenthe outer tank wall and the body of liquid contained within the tank,thus aiding in the conservation of heat and greatly decreasing the heatloss occasioned by conduction through the side walls of the tank. Thesurface of the layer 50 which lies adjacent to the film of coatingmaterial 14 is characterized by an extremely hard and dense surfaceoccasioned byv contact of the mix with the extremely smooth surfacepresented by the coating material 14. In viewing samples of the innerlining material which have been broken away from the tank structure fortest. purposes,

nature of that portion of the layer comprising the strata 51 and 52.While the inner stratum 52 is relatively dense, the same. is nonethelessrelatively soft and of a calcined nature, while the stratum 51 isrelatively hard but of a porous nature, thereby permitting liquidintroduced within the tank body to seep through the pores of the strata51 and 52 to decrease the pressure exerted upon the layer of innerlining materialitself and to dis-' tribute such pressure throughout themajor portion of the inner lining. Yet, at the same time, liquid introbeemployed with equal facility in carrying out the steps of the presentmethod and in producing the end product without departing from thespirit of the invention or the scope of the following claims,

I claim:

1. The -method cementitious lining to a metallic tank having acylindrical body portion and top and bottom closure walls, whichcomprises coating the entire inner surfaces of said'tank with ahardenable phenol-formaledhyde resin; causing said resin to harden;introducing within said tank component parts of a fluid cementitious mixcomprising Portland cement, sand, and water; simultaneously axiallyrotating and tilting said tank about a substantially horizontal axis tothoroughly mix the component parts of said cementitious 'mix within saidtank and to disperse said mix uniformly throughout the length of saidtank; and thereafter axially rotating said tank at relatively high speedand simultaneously vibrating the tank to centrifugally apply and compactthe mix against the inner surfaces of said tank, the vibration ofsaidtank being effected by forces applied to the exterior thereof alongsubstantially its full length, and continuing rotation of said tankuntilsaid mix attains a hardened state.

2. The method of applying a non-frangible, corrosionresistant innerlining to a cylindrical metallic tank which comprises coating the innerwall surface of the tank with a liquid phenol-formaldehyde resin; curingsaid resin to a hardenable state; introducing within said tank thecomponents of a fluid cementitious mix comprising Portland cement, sand,and water; simultaneously rotating and tilting said tank to thoroughlyadmix the componentsof said mix within the tank; axially rotating saidtank at high speed, while maintained in a substantially horizontalplane, and simultaneously vibrating the tank to apply and compact saidmix in a continuous layer against the inner duced within the tank isprevented from contacting the t impervious character of the outersurfaceof the lining layer.

In view of the foregoing, it will be seen that the present inventionprovides an improved and highly efiicient aggregate linedliquid-receiving tank and an eflicient and economical method forproducing the same. Inner-lined tanks formed in accordance with thepresent invention are characterized by their high tensile strength andtheir consequent ability to withstand relatively extreme shock or impactforces without detrimental effect to the inner liner of the tank.Further, by nature of the cementitious aggregate material making up theinner lining of the tank, the same is enabled to withstandthe corrosiveeffect of liquids introduced within the tank by preventing contactbetween such liquids andthe outer metallic shell of the tank,

The invention further provides an eflicient and economical method forlining metallic tank bodies and makes possible the mass production ofsuch inner-lined tanks in relatively short periods of time heretoforethought impossible in view of the relatively extreme length of timerequired in curing cementitious materials. Through the use of the curingaccelerator, the aggregate cementitious mix which comprises the innerlining material may be set in a matter of minutes, and, more important,during the actual application and compaction of the mix against theinner side wall of the tank body, thus eliminating the ordinarily longcuring time required with ordinary cementitious mixes to transform thesame from a plastic state to a completely hardened and, cured state.

While certain forms of apparatus have been disclosed in connection withthe formation and production of the present inner-lined liquid-receivingtank, it will be understood that various types of machines andapparatusmay wall surface of said tank, said tank being vibrated by forcesapplied directly to the exterior thereof throughout substantially itsfull length; and continuing rotation of said tank until the layer of mixattains a hardened state.

3. The method of lining cylindrical metallic bodies which comprisesfirst coating the inner wall surface of a cylindrical metallic body witha film of liquid phenolformaldehyde resin; causing said resin to harden;introducing within said body the components of a fluid cementitious mixcomprising Portland cement, sand, water,

and a curing accelerator for said mix; agitating said body in a mannerto thoroughly admix said components and accelerator within said body;axially rotating said body about a substantially horizontal axis tocentrifugally deposit and compact the mix in a continuous layer upon theinner wall surface of said body; vibrating said body by forces appliedexternally thereto along a line extending substantially throughoutitsfull length and during rotation thereof; and continuing rotation ofsaid body until said mix cures to a hardened state.

4. In the manufacture of an inner-lined hot water I tank, the stepswhich comprise-introducing within an unlined tank the components of afluid cementitious mix comprising Portland cement, sand, water, and acuring accelerator for said mix; agitating said tank to admix saidcomponents and curing accelerator and to disperse the resultant mixuniformly longitudinally of said tank;

thereafter axially rotating said tank at high speed about asubstantially horizontal axis to centrifugally deposit said mix in auniform continuous layer against the inner wall surface of said tank;subjecting said tank uniformly throughout the full length thereof tovibration-imparting cementitious linings on the inner surfaces 'of thecylin- Y drical bodies of water-heating and storage tanks, which ofapplying a corrosion-resistant.

surfaces of the tank body and form on such surfaces a hardened permanentlininghaving walls of substantially uniform thickness, and during saidspinning of the tank applyingv rapidly executed flailing forces to theexterior of the tank body along a line extending substantially the fulllength thereof, whereby to impart uniform vibration to all portions ofsaid body during centrifuging of the lining-forming materials within thetank.

6. The method of lining water-heating and storing tanks composed ofhollow cylindrical bodies having the ends thereof provided with attachedclosure heads, [the steps which comprise] whichcomprises: introducinginto the interior of a head-closed body. of such a-tank the componentsof a plastic Portland cement, sand, and water mix; then rotating saidbody first in one direction and then in the other about its longitudinalaxis and tilting the same back and forth about a transverse axisdisposed intermediately of the tank ;to thoroughly agitate the mix;thereafter spinning the tank about its longitudinal axis [as] at arelan'vely high rate of speed; applying to said body during suchspinning thereof rapidly executed vibratory forces along a lineextending substantially the mu length Ofaaid body; discontinuing saidspinning and opening the tank bodyto drain free water thereform; andthereafter again spinning the tank'about its longitudinalanistofullycompactthesaidmixagainsttheinnerwalls of the tank. 7. Themethod of applying a corrosion-resisting lining to the inner surfaces ofthe of waterheatingand storage tanks, which comprises: introducing thecomponents of a cementitious plastic mix containing Portland cement,sand, water, and a curing accelerator into-the interior ofsuch a tankbody; mixing said com ponents-by tank body about itslongitudinalaxiswhilerock1ng thesamebackandforth about an axistransversely and 'intermediatelyof the tank; thendiscontinuing theoscillation of the" tank bodyaboutsaidt'ramverseaxisandsubiectingthesametoasecond-stageofrotationinwhiehthebodyiscaused interior surfaces" thereof.I v 1 speed rotation of the tank body applying to the exterior thereofrapidly executed flailing forces along a line extending substantiallythe full length of the tank body to cause all parts thereof to vibrateuniformly; discontinuing the flailing and high speed rotation of thebody and removing free water from the interior thereof; and gainsubjecting said body following water removal to high speed spinning toproduce with the presence of said accelerator a hardened and curedcomposite cementitious lining on the inner surfacesof said body, thecombined spinning and flailing operations causing the composition ofsaid mix and thelining formed therefrom to v a smooth, hard,densesurface formation in outer regions thereof disposed immediatelyadjacent said tank 5 body and which is backed by a relatively coarse,rough and porous body formation;

8.- The method of producing centrilugally fanned cementitious liningsonthe inner surfaces of the cylindri- 1 1 7 col of waiter-heating andstoring tanks, which com prises: inrroduducing Portland cement, sand,and water:

' into the interior of a cylindrical tank bodyfand therer afterspinningsuid tank body by rotating the same rapidly a'bout itslongitudinal axis to efiect. substantially uni-1f, form distribution ofthe materials introduced thereinoverfl lhe'inner surfaces of the tankbody, and simultaneously. with said spinning of .the tank body applyingrapidly executed flailing forces to the exterior of the tank body alonga line extending substantially the full length ther'er of, whereby toimpel-{vibration to substantially all portion: ofsaid tank body duringthe centrifugal "application of the materials introducedinto saidReferences cues in the file of this patent or the patent UNrran SIAIES;PATENTS 155,413 Stephens Sept. 29, 1874 I 1,676,815 Beatty July 10, 19281,873,945 -Kraenzlein et al. Aug, 23, 1932 1,932,726 Eolotf et al. Oct.31', 1933 2,148,558 Huebner Feb. 28,1939 2,235,937 Linberg Mar. 25, 19412,395,731 Ford Feb. 26, 1946 2,450,095 Seebold Sept. 2a, 1948 FOREIGNPATENTS I i 277,095 Italy Aug. 29, 193

Great Britain Jan. 13, 1937 tank to the.

